System for preparing and handling multiple laser desorption ionization probes

ABSTRACT

The present invention comprises a system to facilitate sample preparation, common transport, and storage of a plurality of laser desorption ionization probes to be interrogated in a mass spectrometer. The system includes a plurality of probes, a cassette that accepts the plurality of probes, a well-plate that engages the cassette and permits delivery of samples to the probes without fluid communication between samples, and a clamp to secure the well-plate to the cassette. The cassette is configured to constrain the plurality of probes so that the probes suspend from ribs disposed within the cassette. This permits the top and bottom surfaces of the probes to be substantially exposed and facilitates insertion and removal of the probes from the cassette without user contact of active areas on the probes.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. provisional patent application Serial No. 60/359,940, filed Feb. 26, 2002, and U.S. provisional patent application Serial No. 60/374,889, filed Apr. 23, 2002, the disclosures of which are incorporated by reference in their entireties.

FIELD OF THE INVENTION

[0002] The present invention relates to a system for sample preparation, common transport, and storage of multiple laser desorption ionization probes.

BACKGROUND OF THE INVENTION

[0003] Over the past decade, improvements in mass spectrometry (MS) have allowed MS to take a place among standard analytical tools in the study of biologically relevant macromolecules, notably proteins purified from complex biological systems. For example, the development of matrix-assisted laser desorption/ionization approaches has permitted MS analysis to be applied to large molecular weight analytes, including proteins as large as several hundred kilodaltons, while affinity capture laser desorption/ionization approaches have made possible the selective concentration from inhomogeneous samples of desired analytes directly on the laser desorption ionization probe's active surfaces. Improvements in hardware, including control and detection electronics, have led to improved sensitivity, mass accuracy and resolution, while improved software algorithms have improved the ability to use the data so obtained to identify unknown analytes.

[0004] In affinity capture laser desorption ionization, the active surfaces of the laser desorption ionization (LDI) probe are affinity capture surfaces, which are capable of adsorbing analytes selectively from heterogeneous samples, concentrating them on the probe surface in a form suitable for subsequent laser desorption/ionization. The LDI probes are then used to deliver the samples into a mass spectrometer for interrogation by a laser source. Optionally, energy-absorbing (or “matrix”) molecules are applied prior to analysis.

[0005] Affinity capture surfaces of affinity capture laser desorption/ionization probes can include either a chromatographic or a biomolecule affinity moiety. Chromatographic affinity surfaces have an adsorbent capable of chromatographic discrimination among or separation of analytes. Such surfaces can thus include anion exchange moieties, cation exchange moieties, reverse phase moieties, metal affinity capture moieties, and mixed-mode adsorbents, as such terms are understood in the chromatographic arts. Biomolecule affinity surfaces have an adsorbent comprising biomolecules capable of specific binding. Such surfaces can thus include antibodies, receptors, nucleic acids, lectins, enzymes, biotin, avidin, streptavidin, Staph protein A and Staph protein G.

[0006] Liquid samples typically applied to the active surfaces of laser desorption ionization probes, including affinity capture LDI probes, are typically several microliters in volume; after subsequent purification processes, usually only picomoles to nanomoles of analytes remain for analysis in the mass spectrometer.

[0007] With such small quantities of analytes, and with spectrometers having such high sensitivity, contamination of the active surfaces is a major problem in use of LDI probes. Specifically, when an operator handles and transfers the probes, there are numerous opportunities for the operator inadvertently to grasp the LDI probes on or near one or more of its active surfaces (such as affinity capture surfaces)—and consequently, to contaminate the samples thereon with finger proteins, collagen, and dirt. For example, an operator is presently called upon to handle each LDI probe at least three times during the analysis process, providing at least three opportunities to contaminate each probe: once to transfer the LDI probe from a shipping container to a sample preparation platform, once to transfer the LDI probe to a mass spectrometer, and once to transfer the LDI probe to storage. Each successive contact with the LDI probe increases the likelihood of accidental contamination of the active surfaces, and consequent interference with analysis. Since many experimental procedures use numerous probes to obtain statistically relevant data and/or to analyze multiple analytes for comparison, contamination opportunities increase accordingly.

[0008] Thus it would be desirable to provide a system for facilitating sample preparation, common transport, and storage of multiple laser desorption ionization probes that reduces opportunities for accidental operator contamination of the samples.

[0009] It would also be desirable to provide a system for facilitating sample preparation, common transport, and storage of multiple laser desorption ionization probes that would reduce the number of manual operations throughout the mass spectrometric preparation, analysis, and storage process.

[0010] It further would be desirable to provide a system for facilitating sample preparation, common transport, and storage of multiple laser desorption ionization probes that would be compatible with mass spectrometers and ancillary equipment currently used in industry and research facilities.

[0011] It still further would be desirable to provide a system for facilitating sample preparation, common transport, and storage of multiple laser desorption ionization probes having affinity capture surfaces of different types.

SUMMARY OF THE INVENTION

[0012] In view of the foregoing, it is an object of the present invention to provide a system for facilitating sample preparation, common transport, and storage of multiple laser desorption ionization probes that reduces opportunities for accidental operator contamination of the samples.

[0013] It is also an object of the present invention to provide a system for facilitating sample preparation, common transport, and storage of multiple laser desorption ionization probes that would reduce the number of manual operations throughout the mass spectrometric preparation, analysis, and storage process.

[0014] It is a further object of the present invention to provide a system for facilitating sample preparation, common transport, and storage of multiple laser desorption ionization probes that would be compatible with mass spectrometric equipment currently used in industry.

[0015] It is still a further object of the present invention to provide a system for facilitating sample preparation, common transport, and storage of multiple laser desorption ionization probes that would allow each probe to comprise an affinity moiety differing from those of the remaining probes.

[0016] These and other objects of the present invention are accomplished by providing a system comprising, inter alia, a cassette that accepts multiple LDI probes. The cassette transports the multiple LDI probes throughout sample preparation, analysis, and storage without the need for a human operator to remove the LDI probes from the cassette, thereby minimizing, if not eliminating, accidental operator contact of active areas on the probes.

[0017] In a first aspect, therefore, the invention provides a device to removably constrain a plurality of probes, each of the probes having a top surface and a bottom surface, so that the top and bottom surfaces of the constrained probes are substantially exposed, the typical embodiment of the device comprising: a frame having: (a) first, second, third and fourth side members, wherein the first, second, and third side members have coplanar top surfaces and coplanar bottom surfaces, the coplanar surfaces respectively defining a top and a bottom frame plane; and (b) constraining means to constrain the plurality of probes within the frame, the means fully constraining each of the probes in a first frame axis that is orthogonal to said top and bottom frame planes, the means fully constraining each of the probes in a second frame axis that is orthogonal to said first frame axis, and the means slidably constraining each of the probes in a third frame axis that is orthogonal to said first and second frame axes, wherein the constraining means are configured to permit the top and bottom surfaces of probes constrained within the frame to be substantially exposed respectively through the top and bottom frame planes.

[0018] In the typical embodiment, the frame may be substantially rectangular, wherein the first and third side members and the third frame axis are substantially parallel, and the second and fourth side members and second frame axis are substantially parallel. The constraining means may comprise a plurality of ribs integrally formed with the frame, each rib having a longitudinal centerline and a cross section, wherein the longitudinal centerline of each rib is parallel to the third frame axis and orthogonal to the cross section of the rib, wherein the cross section is shaped to mate with a receiving recess of one of the plurality of probes to be constrained within the frame, and wherein adjacent ribs constrain the mated probe fully in the first and second frame axes and slidably in the third frame axis. Furthermore, the plurality of ribs may be disposed so that the active surfaces on the plurality of probes, when constrained within the cassette, are recessed from the top plane of the cassette and the plurality of ribs to further prevent accidental contamination of the samples by inadvertent direct operator contact.

[0019] In a useful embodiment, the cross-section of each rib is shaped as a dovetail so that adjacent ribs form a dovetail mortise therebetween and each rib extends incompletely from the top plane of the frame toward the bottom plane of the frame; as a result, one of the plurality of probes mated thereto suspends between adjacent ribs and is fully constrained in the first frame axis.

[0020] To advance compatibility of the present invention with sample preparation and analysis equipment currently used in industry and research, the placement and number of the active surfaces on the LDI probes, and the number and alignment of LDI probes accepted within the cassette, may be designed to mirror the 8×12 sample deposition configuration of 96 well microtiter plates. Among other things, this allows the present invention to be used with known sample preparation robotics that are designed to deliver fluid samples to a 96 well microtiter plate.

[0021] Furthermore, because the cassette can carry multiple LDI probes, a variety of affinity capture surfaces can be physically associated through sample preparation, analysis, and storage.

[0022] In other embodiments, the cassette further comprises identifying indicia on the frame, typically a barcode.

[0023] In a second aspect, the invention provides probes configured to be removably accepted by the cassette of the present invention having at least one mortise. The probe comprises a rectangular beam having a longitudinal centerline, a top surface, a bottom surface, and two sides parallel to the longitudinal centerline; and a plurality of active surfaces at discretely interrogatable locations disposed along the longitudinal centerline on the top surface of the beam in a fixed spatial relationship, wherein the two sides are undercut to form a tenon therebetween, the tenon slidably engaging the at least one mortise of the device.

[0024] In a typical embodiment, the tenon is dovetail-shaped; in an alternative embodiment, the tenon is I-shaped. In particularly useful embodiments, the plurality of active surfaces are affinity capture surfaces, and the probe further comprises identifying indicia, such as a barcode, disposed on the rectangular beam.

[0025] The probe usefully can further comprise at least one groove disposed orthogonal to the longitudinal centerline to facilitate insertion and removal of said probe from the cassette.

[0026] Further to reduce user contact and manual operations, the system of the present invention also can comprise a well-plate that allows for individual sample deposition to each active surface without fluid communication thereamong. The well-plate is secured to the cassette, within which the LDI probes are constrained, by a clamp. Once the clamp secures the well-plate to the cassette, a gasket integral to the well-plate isolates each active surface from adjacent active surfaces, allowing sample fluid to be individually deposited to each active surface via wells that traverse through the well-plate.

[0027] Thus, in another aspect, the invention provides a device to facilitate application of fluid samples discretely to a plurality of active areas disposed on the top surfaces of a plurality of probes constrained in fixed spatial relationship. The device comprises: (a) a substantially rectangular block having: a top and a bottom surface; four side surfaces substantially orthogonal to the top and bottom surfaces; a plurality of noncommunicating through-holes disposed orthogonal to the block top surface and block bottom surface to permit separate delivery of individual fluid samples discretely to the plurality of active areas; and (b) an integrated seal disposed on the block bottom surface, wherein the seal is capable, when the block is engaged to the plurality of probes, of contacting the top surfaces of the plurality of probes and establishing fluid noncommunication among the plurality of active areas thereof.

[0028] The system can further comprise a non-integral component that engages the block to the plurality of probes.

[0029] In a typical embodiment, the non-integral component comprises: a base plate; and at least one linkage assembly having a medial link and an L-shaped link, the medial link rotatably connecting the L-shaped link to the base plate, wherein the at least one linkage assembly is configured to engage the block to the plurality of probes by rotating the medial and L-shaped links to sandwich the block and the plurality of probes between the L-shaped link and the base plate, the L-shaped link contoured to frictionally engage the at least one contoured ledge to urge the block towards the plurality of probes.

[0030] In certain embodiments, the base plate of the non-integral component comprises a plurality of oblong holes, each oblong hole being parallel to adjacent oblong holes, through which identifying indicia of the probes can be viewed while the probes are engaged.

[0031] Usefully, the probes are engaged in the cassette of the present invention when engaged to the well-plate by action of the non-integral component.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other objects and advantages of the present invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which:

[0033]FIG. 1 illustrates an exploded view of the system of the present invention;

[0034] FIGS. 2A-B depict, respectively, the top and bottom views of a laser desorption ionization probe of the present invention;

[0035] FIGS. 3A-B show, respectively, the top and bottom views of a cassette of the present invention;

[0036]FIG. 4 portrays the laser desorption ionization probe of FIGS. 2A-B constrained within the cassette of FIGS. 3A-B;

[0037] FIGS. 5A-B detail components of the cassette of FIGS. 3A-B;

[0038] FIGS. 6A-C illustrate, respectively, top, bottom, and partial side views of a well-plate of the present invention;

[0039]FIG. 7 depicts a clamp of the present invention;

[0040]FIG. 8A shows an alternative embodiment of the laser desorption ionization probe of the present invention;

[0041]FIG. 8B portrays the laser desorption ionization probe of FIG. 8A constrained within an alternative embodiment of the cassette of the present invention;

[0042]FIG. 9 illustrates a second alternative embodiment of the cassette of the present invention;

[0043]FIG. 10 shows a second alternative embodiment of the laser desorption ionization probe of the present invention; and

[0044] FIGS. 11A-B respectively portray close-up perspective and top views of a third alternative embodiment of the cassette of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0045] Referring to FIG. 1, system 10 of the present invention is illustrated, comprising a cassette 20, a plurality of laser desorption ionization (LDI) probes 40, a well-plate 60, and a clamp 80. System 10 facilitates sample preparation, common transport, and storage of the plurality of LDI probes. When cassette 20, LDI probes 40, well-plate 60, and clamp 80 are integrated, an operator or known sample preparation robot may deposit fluid samples onto LDI probes 40 constrained within cassette 20 via well-plate 60 without fluid communication among the samples. Without clamp 80 and well-plate 60, the operator may use cassette 20 to commonly transport and store LDI probes 40 without the need to remove the probes from the cassette, decreasing the opportunities for the operator to contaminate the samples by inappropriately grasping LDI probes 40.

[0046] Detailed in FIGS. 2A-B, LDI probe 40 comprises a rectangular bar 41, extruded from an electrically conductive material such as aluminum. Alternatively, rectangular bar 41 may be molded from conductive plastic, or machined from a conductive material such as tantalum. Further alternatively, rectangular bar 41 made be made from a non-conductive material, such as glass. Rectangular bar 41 optionally undergoes machining and/or chemical derivatization operations to form discrete active surfaces 42 on top surface 46. The active surfaces are capable of being separately interrogated by a mass spectrometer (not shown) during analysis; in certain embodiments, the active surfaces are affinity capture surfaces. In a useful embodiment, LDI probe 40 comprises eight active surfaces. Machining operations also form groove 43, which spans the width 44 of LDI probe 40 and facilitates insertion and removal of LDI probe 40 from cassette 20.

[0047] In a typical embodiment, LDI probe 40 comprises undercuts 45 that form a dovetail tenon therebetween. The dovetail tenon may slide into one of a plurality of dovetail mortises disposed within cassette 20. LDI probe 40 further optionally comprises identifying indicia 47 which may be disposed on bottom surface 48 of LDI probe 40. Identifying indicia may include but are not limited to bar codes, magnetically-coded indicia, radiofrequency indicia (RFID tags) or other indicia known in the art that are capable of storing information. Identifying indicia may be used, inter alia, to identify the type of active surfaces on LDI probe 40, and identify an analysis protocol associated with LDI probe 40. It further may be used to provide tracking and sample information, and to provide a unique identifier to associate results of analysis.

[0048] Cassette 20, shown in FIGS. 3A-B, accepts a plurality of LDI probes 40. In a useful embodiment, cassette 20 may carry up to twelve LDI probes. Since probes readily can comprise eight active surfaces 42, the resulting 8×12 matrix in this embodiment matches a standard 96 well microtiter configuration, permitting the present invention to interface with known sample preparation instrumentation, such as sample preparation robotics. Of course, one of ordinary skill in the art will recognize that LDI probe 40 and cassette 20 are not limited to the number of active surfaces and probes indicated hereinabove.

[0049] LDI probes 40 may be inserted into slots 21, which are defined by ribs 22 and half-ribs 23 that are, in a typical embodiment, integrally formed with cassette 20. In the typical embodiment, each rib 22 comprises a dovetail-shaped cross-section; whereas each half-rib 23, integral with the cassette along its entire longitudinal length, comprises half a dovetail-shaped cross-section since each half-rib accepts only one LDI probe 40. Each two adjacent ribs 22, or alternatively one rib 22 and one adjacent half-rib 23, form a dovetail mortise between which the dovetail tenon integral with LDI probe 40 may be inserted. Thus, ribs 22 and half-ribs 23 permit LDI probes 40 to slidably suspend therefrom, the resulting dovetail joint fully constraining LDI probe 40 in the X and Z axes and slidably constraining LDI probe 40 in the Y axis. FIG. 4 depicts a cross-sectional view of LDI probe 40 inserted between one rib 22 and one half-rib 23.

[0050] To increase constraints on LDI probes 40 in direction Y, a plurality of frictional retaining features, comprising linear projections 24 and conical projections 30, are disposed on ribs 22 and half-ribs 23. Projections 24 and 30, which are depicted in greater detail in FIGS. 5A-B, urge LDI probes 40 against cassette 20, increasing the normal forces therebetween. Increased normal forces between LDI probes 40 and cassette 20 increase the frictional forces therebetween, preventing LDI probes 40 from sliding out of slots 21 absent an external force that can overcome the increased frictional forces. Projections 24 and 30 may be integrally molded with cassette 20 or affixed to cassette 20 in a separate manufacturing operation. Note that LDI probes 40 may only be inserted into cassette 20 from one side of the cassette due to back wall 31 disposed integral with cassette 20. Thus, while projections 24 and 30 effectively may slidably constrain LDI probes 40 in both the positive and negative directions of the Y-axis, projections 24 and 30 only need to do so in one direction. Furthermore, one of ordinary skill in the art will recognize that projections 24 and 30 may be disposed anywhere along the longitudinal length of ribs 22 and half-ribs 23. Additional configurations of projections that increase frictional forces between LDI probes 40 and cassette 20 will be apparent to one or ordinary skill in the art.

[0051] In a useful embodiment, ribs 22 are disposed so that, when LDI probes 40 are inserted within slots 21, the longitudinal centerline of each LDI probe is 8-10 mm, inclusive, from the longitudinal centerlines of adjacent LDI probes. Again, this ensures that the present invention is compatible with sample preparation robotics and sample preparation instrumentation currently used in industry. Ribs 22 also are disposed to recess top surfaces 46 of LDI probes 40 when constrained within cassette 20 to further protect the active areas from accidental operator contact.

[0052] Cassette 20 further comprises a plurality of alignment indentations 26, alignment pins 27, and alignment holes 28. Alignment indentations 26 (see FIG. 3B) are used in conjunction with a complementary alignment tab (not shown) disposed on the aforementioned external mechanical device or a mass spectrometer to position an appropriate slot 21 relative thereto for either insertion or removal of one LDI probe 40 from cassette 20. Advantageously, this permits cassette 20 to be manufactured with less rigid tolerance levels while still permitting precise alignment of slots 21. Alignment pins 27 complement alignment holes 28, allowing each cassette to be stacked on top of another cassette in a predetermined manner. This provides for easy shipping, transport, and storage of multiple cassettes 20 carrying multiple LDI probes 40. Additional alignment holes and pins may be incorporated as needed, for example, to facilitate alignment with an external mechanical device or an analytical instrument, e.g., mass spectrometer.

[0053] To provide a means to identify cassette 20, one or more identifying indicia 29 may be disposed on the outside thereof. Indicia may include but are not limited to bar codes, magnetically-coded indicia, radiofrequency indicia (RFID tags) or other indicia known in the art that are capable of storing information. Indicia 29 may provide information about the number, positions and analytical information of LDI probes 40 carried within cassette 20, and/or the order in which the LDI probes are to be analyzed. Indicia 29 also may be used to provide tracking information, and to provide a unique identifier to associate results of analysis.

[0054] Cassette 20 may further comprise handles 32 to facilitate transport thereof. This permits the operator to grasp the cassette remote from active surfaces 42, decreasing the opportunities to contaminate the samples.

[0055] Cassette 20 may be injection molded. In a useful embodiment, cassette 20 may be injection molded from a polymer optionally filled with glass inclusions, e.g., glass-filled polypropylene, in which the glass inclusions enhance rigidity of the cassette. Advantageously, polypropylene permits the cassette to be carried through chemical reaction baths, such as those that may be used in certain procedures to manufacture the LDI probes and/or process and analyze samples deposited upon or disposed within the LDI probes. Indeed, if cassette 20 is made at least in part from polypropylene or another chemically suitable material, LDI probes may undergo manufacturing processes, sample deposition/disposition, sample processing, and/or sample analysis without having to be removed from the cassette, thereby decreasing the opportunities for sample contamination, increasing efficiency, and decreasing the number of manual operations to be performed by an operator. As would be evident to one of ordinary skill in the art, cassette 20 also may be manufactured out of other suitable materials.

[0056] To facilitate removal of the cassette from the mold, the sides of cassette 20 usefully may comprise a draft of approximately 0.5-2 degrees. Thus, while the cassette profile is not strictly rectangular, it is still substantially so. Additionally, it will be apparent to one skilled in the art that cassette 20 need not be substantially rectangular. Rather, the sides of cassette 20 may be rounded, angled, or comprise a myriad of configurations without departing from the invention

[0057] The ability to constrain LDI probes 40 within cassette 20 using the features described hereinabove provides numerous advantages. First, because LDI probes 40 are constrained by engagement of the sides of the probes, cassette 20 can substantially expose the top and bottom surfaces of LDI probes 40. Exposure of the top surfaces of LDI probes 40 allows a plurality of samples to be deposited and processed on the LDI probes without the need to remove the probes from cassette 20, thereby decreasing the opportunities to contaminate the samples and reducing the number of manual operations. Exposure of the bottom surfaces of LDI probes 40 allow an indicia reader (not shown) ready access to identifying indicia 47 on the probes.

[0058] Second, the configuration permits ready insertion of probes 40 into cassette 20 without obligating touching and consequently contaminating active surfaces 42. Specifically, ribs 22 and half-ribs 23, along with ready access to grooves 43 on bottom surfaces 48, allow an operator or a separate mechanical device, such as a loading device that automatically transfers multiple LDI probes 40 between a cassette 20 and an analytical instrument, to easily slide LDI probes into or out of cassette 20 in one continuous operation by engaging grooves 43. An illustrative loading device suitable for use with the present invention is described in greater detail in co-pending, to be commonly-assigned U.S. patent application Ser. No. ______ (Attorney Docket No. CiphBio-002), filed Feb. 25, 2003, and U.S. provisional patent application Serial No. 60/374,889, filed Apr. 23, 2002, the disclosures of which are incorporated by reference in their entireties.

[0059] To deposit samples onto active surfaces 42 when LDI probes 40 are constrained within cassette 20, well-plate 60 and clamp 80, respectively shown in FIGS. 6A-C and 7, can be used. Well-plate 60 comprises a plurality of wells 61, each well comprising a through-hole to facilitate deposition of a fluid sample onto one active surface 42. A gasket 62, that is integral with well-plate 60, seals each active surface 42 from adjacent surfaces 42 so that there is fluid noncommunication thereamong. Wells 61 and gasket 62 protrude beyond the sides of well-plate 60, as shown in FIG. 6C, to contact surfaces 46 of LDI probes 40, which are recessed within cassette 20.

[0060] To position well-plate 60 relative to cassette 20 so that each well 61 contacts the appropriate active surface 42, alignment holes 28 on the bottom face of well-plate 60 are disposed to mate with alignment pins 27 on cassette 20. Alternatively, well-plate 60 may contain alignment pins disposed to mate alignment holes in cassette 20.

[0061] Like cassette 20, well-plate 60 may be injection molded from a polymer, e.g., a mixture of thermoplastic elastomer and polypropylene homopolymer, which advantageously provides chemical compatibility and decreases protein adsorption. One of ordinary skill in the art will recognize that other suitable materials also may be used, e.g., polycarbonate or polystyrene. If well-plate is injection molded, the sides of well-plate 60 usefully may, in such case, comprise a draft of approximately 0.5-2 degrees to facilitate removal of the well-plate from the mold. Furthermore, similar to cassette 20, it will be apparent to one skilled in the art that well-plate 60 need not be substantially rectangular. Rather, the sides of the well-plate may be rounded, angled, or comprise a myriad of configurations without departing from the invention.

[0062] To secure well-plate 60 to cassette 20 for sample deposition, clamp 80 can be used. Clamp 80 comprises two linkage assemblies defined by a common base plate 81, which is rotatably connected to middle links 82, which in turn are rotatably connected to L-shaped links 83. Each L-shaped link 83 comprises a base bar 85 and two prongs 86. Side 87 of base bar 85 is contoured to rotatably engage contoured ledge 63, which is integrally formed with well-plate 60. Clamp 80 employs what is commonly known as an “over-center” mechanism. When clamp 80 is fully engaged, the forces of engagement are positioned such that the opposing or opening forces cause tightening torques. Gasket 62 provides the necessary compressive compliance.

[0063] In operation, cassette 20, carrying LDI probes 40, is stacked between base plate 81 and well-plate 60. Middle links 82 and L-shaped links 83 are swung about to partially enclose cassette 20 and well-plate 60 between prongs 86 and base plate 81. Sides 87 are then positioned to rotatably engage ledges 63 on well-plate 60, and pressure is applied to prongs 86. The pressure thus applied secures well-plate 60 to cassette 20, engaging gasket 62 to top surfaces 46 of LDI probes 40 and isolating each active surface 42 from adjacent active surfaces. In the final secured position, prongs 86 rest parallel to base plate 81. Once sample deposition has been completed, clamp 80 may be released by engaging prongs 86 via thumb holes 64 and counter-swinging L-shaped links 83 and middle links 82 away from well-plate 60 and cassette 20. Cassette 20, carrying a plurality of active LDI probes 40, then may be removed to the mass spectrometer (not shown) for laser interrogation of each active surface 42.

[0064] Base plate 81 further comprises a plurality of milled cutouts 84, typically oblong, that expose identifying indicia 47 affixed to LDI probes 40 when the probes are engaged in cassette 20 sandwiched between base plate 81 and well-plate 60. This permits an indicia reader to access identifying indicia 47 and retrieve information associated with each probe. For example, this allows sample preparation equipment, such as sample preparation robotics, to obtain information about each LDI probe 40 so that the appropriate sample will be delivered to each active surface 42.

[0065] Again, while FIGS. 1 and 7 illustrate a form factor that accepts a substantially rectangular cassette and well-plate, clamp 80 may be modified to accept different shapes of cassette 20 and well-plate 60 without departing from the invention.

[0066] Clamp 80 may be made from aluminum, die-cast zinc, or another sufficiently rigid material.

[0067] Referring to FIGS. 8A-B, an alternative embodiment of LDI probe 140 is illustrated in which undercuts 145 form an I-shaped tenon rather than a dovetail tenon. Accordingly, the cross sections of cassette ribs 122 and half-ribs 123 also are modified so that each rib 122 comprises an inverted T-shaped cross section and each half-rib 123 comprises half an inverted T-shaped cross section so that T-shaped mortises are formed between adjacent ribs and/or half-ribs. The T-shaped mortises then may slidably accept the I-shaped tenons of LDI probes 140, fully constraining LDI probes 140 in the X and Z axes and slidably constraining LDI probes 140 in the Y axis. Of course one of ordinary skill in the art will recognize that the cross-sections of the ribs, the half-ribs, and the LDI probes are not limited to those presented in FIGS. 4 and 8B. Rather, they may comprise any cross-section that permits the LDI probes to suspend between adjacent ribs and/or half-ribs so that the probes are fully constrained in the X and Z axes and slidably constrained in the Y axis.

[0068] Referring to FIG. 9, a second alternative embodiment of the cassette of the present invention is described. This alternative embodiment also substantially exposes the bottom surfaces of LDI probes 240 constrained within cassette 220 in order to facilitate insertion and removal of the probes from the cassette and to expose identifying indicia 47 disposed on each probe's bottom surface. However, rather than solely relying on ribs 22 or 122 to constrain LDI probes 40 or 140 in the −Z direction, the present embodiment comprises a cross bar 201, which is disposed across the underside of cassette 220 so that LDI probes 240 are inserted between ribs 222 and cross bar 201. Accordingly, while ribs 222 may still comprise a cross-section that permits LDI probes 240 to suspend therefrom, the present embodiment no longer necessitates it since cross bar 201 will constrain LDI probes 240 in the −Z direction. Ribs 222 now may comprise a rectangular cross section. Accordingly, the cross section of LDI probe 40 also may change to accommodate the altered cross section of ribs 222, for example, as shown in FIG. 10. The cross-section of LDI probe 40 further may be altered to comprise a rectangle having top and bottom surfaces that are wider than the width of the slot defined by adjacent ribs 222. Such rectangular probes may be slidably disposed between ribs 222 and cross bar 201, and constrained in the X-axis by projections that may be disposed on ribs 222 to separate adjacent probes when the probes are inserted and constrained in the cassette. These projections may be similar to projections 24 of FIG. 5B.

[0069] With the introduction of cross bar 201 across the underside of cassette 220, LDI probe 240 may comprise a second groove 243 in addition to groove 43 to facilitate slidable insertion and removal of LDI probe 240 from cassette 220. For example, to insert LDI probe 240, second groove 243 is initially engaged to push LDI probe 240 into slot 221. Once groove 43 clears cross bar 201, second groove 243 is disengaged, and groove 43 is engaged to pull LDI probe 240 fully into cassette 220. Ribs 222 along with cross bar 201 fully constrain LDI probes 240 in the Z axis.

[0070] Cross-bar 201 also may be disposed in an alternative location or additional cross-bars may be employed. For example, a cassette comprising ribs 122 and half-ribs 123 described with respect to FIG. 8B, also slidably may accept LDI probes having T-shaped cross sections, in which the top surfaces of the probes having the plurality of active surfaces are wider than the bottom surfaces. To help constrain the probes in the Z-direction, cross-section 201 may be relocated across the top surface of the cassette.

[0071] Referring respectively to FIGS. 11A-B, close up perspective and top views of a third alternative embodiment of the cassette of the present invention are described in which the frictional retaining features of the cassette differ from those of the other embodiments. Rather than or in addition to having both linear projections 24 and conical projections 30, the third embodiment comprises alternative projections 301. Projections 301 comprise one or more lobes that are disposed on ribs 322 and the half-ribs (not shown), which narrow into necks 302 at projections 301. Like projections 24 and 30, projections 301 increase the frictional forces between the probes and the cassette and may also be disposed anywhere along the length of ribs 322 and the half-ribs.

[0072] Although illustrative embodiments of the present invention are described above, it will be apparent to one skilled in the art that various changes and modifications may be made without departing from the invention. It is intended in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the invention. 

What is claimed is:
 1. A device to removably constrain a plurality of probes, each of the probes having a top surface and a bottom surface, so that the top and bottom surfaces of the constrained probes are substantially exposed, the device comprising: a frame having: (a) first, second, third and fourth side members, wherein said first, second, and third side members have coplanar top surfaces and coplanar bottom surfaces, the coplanar surfaces respectively defining a top and a bottom frame plane; and (b) constraining means to constrain the plurality of probes within said frame, said means fully constraining each of the probes in a first frame axis that is orthogonal to said top and bottom frame planes, said means fully constraining each of the probes in a second frame axis that is orthogonal to said first frame axis, and said means slidably constraining each of the probes in a third frame axis that is orthogonal to said first and second frame axes, wherein said constraining means are configured to permit the top and bottom surfaces of probes constrained within said frame to be substantially exposed respectively through the top and bottom frame planes.
 2. The device of claim 1, wherein said constraining means comprise a plurality of ribs integrally formed with said frame, each rib having a longitudinal centerline and a cross section, wherein the longitudinal centerline of each said rib is parallel to said third frame axis and orthogonal to the cross section of said rib, wherein the cross section is shaped to mate with a receiving recess of one of the plurality of probes to be constrained within said frame, and wherein adjacent said ribs constrain the mated probe fully in said first and second frame axes and slidably in said third frame axis.
 3. The device of claim 2, wherein the cross-section of each said rib is shaped as a dovetail so that adjacent ribs form a dovetail mortise therebetween.
 4. The device of claim 2, wherein the cross-section of each said rib is an inverted T-shape so that adjacent said ribs form a T-shaped mortise therebetween.
 5. The device of any one of claims 2-4 wherein each said rib extends incompletely from the top plane of said frame toward the bottom plane of said frame, whereby each of the plurality of probes mated thereto is suspended between adjacent said ribs and is fully constrained in said first frame axis.
 6. The device of claim 2, wherein said plurality of ribs are disposed to recess at least the top surface of each of the probes constrained within said frame.
 7. The device of claim 1, wherein said constraining means comprises a cross bar integrally formed with and connecting said first and third frame side members, said cross bar having a bottom surface coplanar with the bottom frame plane, wherein said cross bar is configured to permit the bottom surface of the probes constrained within said frame to be substantially exposed through the bottom frame plane.
 8. The device of claim 1, further comprising means for frictionally securing the probes slidably in said third frame axis.
 9. The device of claim 8, wherein said frictional means comprises a plurality of projections disposed on said frame that increases the normal forces between each constrained probe and said frame.
 10. The device of claim 2, wherein the longitudinal centerline of each said rib is a predetermined distance away from the longitudinal centerlines of adjacent ribs.
 11. The device of claim 10, wherein the predetermined distance is within the range of 8 to 10 mm, inclusive.
 12. The device of claim 1, wherein said device can constrain up to 12 probes within said frame.
 13. The device of claim 2, further comprising a plurality of alignment indentations disposed on said frame, each alignment indentation disposed between successively adjacent said ribs to facilitate alignment of said frame for insertion and removal of one of the plurality of probes.
 14. The device of claim 1, further comprising means to stack said frame.
 15. The device of claim 14, wherein said stacking means comprise: a plurality of alignment pins protruding from said frame; and a plurality of alignment holes blindly boring into said frame, wherein each said alignment hole is disposed concentrically with and spatially distant to each said alignment pin.
 16. The device of claim 1, further comprising identifying indicia on said frame.
 17. The device of claim 16, wherein said identifying indicia is a barcode.
 18. The device of claim 1, wherein: said frame is substantially rectangular; said first and third side members and said third frame axis are substantially parallel; and said second and fourth side members and said second frame axis are substantially parallel.
 19. A probe to be removably accepted by a device having at least one mortise, the probe comprising: a substantially rectangular beam having a longitudinal centerline, a top surface, a bottom surface, and two sides parallel to the longitudinal centerline; and a plurality of active surfaces at discretely interrogatable locations disposed along the longitudinal centerline on the top surface of said beam in a fixed spatial relationship, wherein the two sides are undercut to form a tenon therebetween, said tenon slidably engaging the at least one mortise of the device.
 20. The probe of claim 19, wherein said tenon is dovetail-shaped.
 21. The probe of claim 19, wherein said tenon is I-shaped.
 22. The probe of claim 19, wherein said rectangular beam comprises electrically conductive material.
 23. The probe of claim 19, wherein said plurality of active surfaces are affinity capture surfaces.
 24. The probe of claim 19, wherein said plurality of active surfaces comprise eight active surfaces.
 25. The probe of claim 19, further comprising identifying indicia disposed on said rectangular beam.
 26. The probe of claim 25, wherein said identifying indicia is a barcode.
 27. The probe of claim 19, further comprising a groove disposed orthogonal to the longitudinal centerline to facilitate insertion and removal of said probe from the cassette.
 28. The probe of claim 27, wherein said groove is disposed on the bottom surface of said beam.
 29. The probe of claim 27, further comprising a second groove disposed orthogonal to the longitudinal centerline to facilitate insertion and removal of said probe from the cassette.
 30. A device to facilitate application of fluid samples discretely to a plurality of active areas disposed on the top surfaces of a plurality of probes constrained in fixed spatial relationship, the device comprising: a block having: a top and a bottom surface; four side surfaces; a plurality of noncommunicating through-holes disposed orthogonal to the block top surface and block bottom surface to permit separate delivery of individual fluid samples discretely to the plurality of active areas; and an integrated seal disposed on the block bottom surface, wherein said seal is capable, when said block is engaged to the plurality of probes, of contacting the top surfaces of the plurality of probes and establishing fluid noncommunication among the plurality of active areas thereof.
 31. The device of claim 30, further comprising at least one contoured ledge disposed on at least one of the side surfaces.
 32. The device of claim 31, further comprising a non-integral component to engage said block to the plurality of probes.
 33. The device of claim 32, wherein said engaging component comprises: a base plate; and at least one linkage assembly having a medial link and a L-shaped link, said medial link rotatably connecting said L-shaped link to said base plate, wherein said at least one linkage assembly is configured to engage said block to the plurality of probes by rotating said medial and L-shaped links to sandwich said block and the plurality of probes between said L-shaped link and said base plate, said L-shaped link contoured to rotatably engage said at least one contoured ledge to urge said block towards the plurality of probes.
 34. The device of claim 33, wherein said base plate comprises a plurality of holes, each hole parallel to adjacent oblong holes.
 35. The device of claim 33, wherein said L-shaped link comprises: a first bar; and two second bars integral with and non-coplanar to said first bar at longitudinally opposing ends of said first bar.
 36. The device of claim 33, wherein said medial link rotatably connects said first bar to said base plate.
 37. The device of claim 33, wherein said medial link comprises two bars, each of said bars rotatably connected to said first bar at longitudinally opposing ends of said first bar.
 38. The device of claim 32, further comprising a plurality of indentations disposed on the side surfaces of said block to facilitate removal of said engaging component.
 39. The device of claim 30, further comprising a frame to removably constrain the plurality of probes during engagement with said block.
 40. The device of claim 39, wherein said frame comprises: first, second, third and fourth side members, wherein said first, second, and third side members have coplanar top surfaces and coplanar bottom surfaces, the coplanar surfaces respectively defining a top and a bottom frame plane; and constraining means to constrain the plurality of probes within said frame, said means fully constraining each of the probes in a first frame axis that is orthogonal to said top and bottom frame planes, fully constraining each of the probes in a second frame axis that is orthogonal to said first frame axis, said means slidably constraining each of the probes in a third frame axis that is orthogonal to said first and second frame axes, wherein said constraining means are configured to permit the top and bottom surfaces of probes constrained within said frame to be substantially exposed respectively through the top and bottom frame planes.
 41. The device of claim 40, wherein: said frame is substantially rectangular; said first and third side members and said third frame axis are substantially parallel; said second and fourth side members and said second frame members are substantially parallel; said block is substantially rectangular; and the side block surfaces are substantially orthogonal to the top and bottom block surfaces.
 42. The device of claim 39, further comprising: a plurality of alignment pins disposed on said frame; and a plurality of alignment holes disposed on the bottom surface of said block, wherein said plurality of alignment pins complement said plurality of alignment holes to constrain said frame and said block in a fixed spatial relationship.
 43. A system for facilitating sample preparation, transport into a mass spectrometer, and subsequent storage, the system comprising: a plurality of probes to accept the samples at discretely interrogatable locations disposed in a fixed spatial relationship, each probe having substantially flat top and bottom surfaces; and a frame having: (a) first, second, third and fourth side members, wherein said first, second, and third side members have coplanar top surfaces and coplanar bottom surfaces, the coplanar surfaces respectively defining a top and a bottom frame plane; and (b) constraining means to constrain the plurality of probes within said frame, said means fully constraining each of the probes in a first frame axis that is orthogonal to said top and bottom frame planes, fully constraining each of the probes in a second frame axis that is orthogonal to said first frame axis, said means slidably constraining each of the probes in a third frame axis that is orthogonal to said first and second frame axes, wherein said constraining means are configured to permit the top and bottom surfaces of probes constrained within said frame to be substantially exposed respectively through the top and bottom frame planes.
 44. The system of claim 43, wherein 12 said probes are constrained within said frame.
 45. The device of claim 43, wherein: said frame is substantially rectangular; said first and third side members and said third frame axis are substantially parallel; and said second and fourth side members and said second frame axis are substantially parallel.
 46. A device to removably constrain a plurality of probes, each of the probes having a top surface and a bottom surface, so that the top and bottom surfaces of the constrained probes are substantially exposed, the device comprising: a frame having: (a) first, second, third and fourth side members, wherein said first, second, and third side members have coplanar top surfaces and coplanar bottom surfaces, the coplanar surfaces respectively defining a top and a bottom frame plane; and (b) a plurality of ribs coupled to said frame, said plurality of ribs shaped to constrain the plurality of probes within said frame, said plurality of ribs fully constraining each of the probes in a first frame axis that is orthogonal to said top and bottom frame planes, said plurality of ribs fully constraining each of the probes in a second frame axis that is orthogonal to said first frame axis, and said plurality of ribs slidably constraining each of the probes in a third frame axis that is orthogonal to said first and second frame axes, wherein said plurality of ribs are configured to permit the top and bottom surfaces of probes constrained within said frame to be substantially exposed respectively through the top and bottom frame planes. 